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author Nigel Barnes <Pernod70@users.noreply.github.com>2022-05-15 16:15:00 +0100
committer Nigel Barnes <Pernod70@users.noreply.github.com>2022-05-15 16:15:00 +0100
commit3377ee1d7985fe6a2b4d79dd5d75c828bccbbbc2 (patch)
tree2b11cf96911a5ea38ae073f398d5fcdecc4dbaf6
parent74728bc4d42ba21de9a58ad0442a413575e7e357 (diff)
bus/bbc/internal: Added the Memex-B20 board.
-rw-r--r--scripts/src/bus.lua2
-rw-r--r--src/devices/bus/bbc/internal/internal.cpp2
-rw-r--r--src/devices/bus/bbc/internal/memex.cpp109
-rw-r--r--src/devices/bus/bbc/internal/memex.h50
4 files changed, 163 insertions, 0 deletions
diff --git a/scripts/src/bus.lua b/scripts/src/bus.lua
index 3a97d6e7c52..b1f17f54e3f 100644
--- a/scripts/src/bus.lua
+++ b/scripts/src/bus.lua
@@ -551,6 +551,8 @@ if (BUSES["BBC_INTERNAL"]~=null) then
MAME_DIR .. "src/devices/bus/bbc/internal/cumana68k.h",
MAME_DIR .. "src/devices/bus/bbc/internal/integrab.cpp",
MAME_DIR .. "src/devices/bus/bbc/internal/integrab.h",
+ MAME_DIR .. "src/devices/bus/bbc/internal/memex.cpp",
+ MAME_DIR .. "src/devices/bus/bbc/internal/memex.h",
MAME_DIR .. "src/devices/bus/bbc/internal/morleyaa.cpp",
MAME_DIR .. "src/devices/bus/bbc/internal/morleyaa.h",
MAME_DIR .. "src/devices/bus/bbc/internal/overlay.cpp",
diff --git a/src/devices/bus/bbc/internal/internal.cpp b/src/devices/bus/bbc/internal/internal.cpp
index b09f6fca29c..a365b5729dc 100644
--- a/src/devices/bus/bbc/internal/internal.cpp
+++ b/src/devices/bus/bbc/internal/internal.cpp
@@ -162,6 +162,7 @@ WRITE_LINE_MEMBER(bbc_internal_slot_device::irq6502_w)
#include "atpl.h"
#include "cumana68k.h"
#include "integrab.h"
+#include "memex.h"
#include "morleyaa.h"
#include "overlay.h"
#include "peartree.h"
@@ -186,6 +187,7 @@ void bbcb_internal_devices(device_slot_interface &device)
device.option_add("atplsw", BBC_ATPLSW); /* ATPL Sidewise ROM/RAM expansion */
device.option_add("cumana68k", BBC_CUMANA68K); /* Cumana 68008 Upgrade Board */
device.option_add("integrab", BBC_INTEGRAB); /* Computech Integra-B */
+ device.option_add("memexb20", BBC_MEMEXB20); /* Memex-B20 RAM expansion */
device.option_add("mr3000", BBC_MR3000); /* Peartree MR3000 ROM board */
device.option_add("mr4200", BBC_MR4200); /* Peartree MR4200 RAM board */
device.option_add("mr4300", BBC_MR4300); /* Peartree MR4300 ROM/RAM board */
diff --git a/src/devices/bus/bbc/internal/memex.cpp b/src/devices/bus/bbc/internal/memex.cpp
new file mode 100644
index 00000000000..809313e4c68
--- /dev/null
+++ b/src/devices/bus/bbc/internal/memex.cpp
@@ -0,0 +1,109 @@
+// license:BSD-3-Clause
+// copyright-holders:Nigel Barnes
+/**********************************************************************
+
+ Memex B20 20K RAM expansion
+
+ This is a DIY project from the May 1984 issue of Electronics and
+ Computing, with part two of the project in the August 1984 issue.
+
+**********************************************************************/
+
+
+#include "emu.h"
+#include "memex.h"
+
+
+//**************************************************************************
+// DEVICE DEFINITIONS
+//**************************************************************************
+
+DEFINE_DEVICE_TYPE(BBC_MEMEXB20, bbc_memexb20_device, "bbc_memexb20", "Memex-B20 RAM expansion");
+
+
+//-------------------------------------------------
+// ROM( memexb20 )
+//-------------------------------------------------
+
+ROM_START(memexb20)
+ ROM_REGION(0x2000, "exp_rom", 0)
+ ROM_LOAD("memex-b20_v2.2.rom", 0x0000, 0x2000, CRC(98ee8eb6) SHA1(aad311797e204b0b69450460f8b4605409c31ddd))
+ROM_END
+
+//-------------------------------------------------
+// rom_region - device-specific ROM region
+//-------------------------------------------------
+
+const tiny_rom_entry *bbc_memexb20_device::device_rom_region() const
+{
+ return ROM_NAME(memexb20);
+}
+
+
+//**************************************************************************
+// LIVE DEVICE
+//**************************************************************************
+
+//-------------------------------------------------
+// bbc_memexb20_device - constructor
+//-------------------------------------------------
+
+bbc_memexb20_device::bbc_memexb20_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
+ : device_t(mconfig, BBC_MEMEXB20, tag, owner, clock)
+ , device_bbc_internal_interface(mconfig, *this)
+ , m_shadow(false)
+{
+}
+
+//-------------------------------------------------
+// device_start - device-specific startup
+//-------------------------------------------------
+
+void bbc_memexb20_device::device_start()
+{
+ address_space &program = m_maincpu->space(AS_PROGRAM);
+
+ program.install_write_handler(0xd000, 0xd000, write8smo_delegate(*this, FUNC(bbc_memexb20_device::enable_w)));
+ program.install_write_handler(0xc000, 0xc000, write8smo_delegate(*this, FUNC(bbc_memexb20_device::disable_w)));
+
+ m_ram = make_unique_clear<uint8_t[]>(0x5000);
+
+ /* register for save states */
+ save_item(NAME(m_shadow));
+ save_pointer(NAME(m_ram), 0x5000);
+}
+
+
+//**************************************************************************
+// IMPLEMENTATION
+//**************************************************************************
+
+void bbc_memexb20_device::enable_w(uint8_t data)
+{
+ m_shadow = true;
+}
+
+void bbc_memexb20_device::disable_w(uint8_t data)
+{
+ m_shadow = false;
+}
+
+uint8_t bbc_memexb20_device::ram_r(offs_t offset)
+{
+ uint8_t data = 0xff;
+
+ if (m_shadow && offset >= 0x3000)
+ data = m_ram[offset - 0x3000];
+ else
+ data = m_mb_ram->pointer()[offset];
+
+ return data;
+}
+
+void bbc_memexb20_device::ram_w(offs_t offset, uint8_t data)
+{
+ if (m_shadow && offset >= 0x3000)
+ m_ram[offset - 0x3000] = data;
+ else
+ m_mb_ram->pointer()[offset] = data;
+}
diff --git a/src/devices/bus/bbc/internal/memex.h b/src/devices/bus/bbc/internal/memex.h
new file mode 100644
index 00000000000..1e4f07bcb16
--- /dev/null
+++ b/src/devices/bus/bbc/internal/memex.h
@@ -0,0 +1,50 @@
+// license:BSD-3-Clause
+// copyright-holders:Nigel Barnes
+/**********************************************************************
+
+ Memex B20 20K RAM expansion
+
+**********************************************************************/
+
+
+#ifndef MAME_BUS_BBC_INTERNAL_MEMEX_H
+#define MAME_BUS_BBC_INTERNAL_MEMEX_H
+
+#include "internal.h"
+
+
+//**************************************************************************
+// TYPE DEFINITIONS
+//**************************************************************************
+
+class bbc_memexb20_device : public device_t, public device_bbc_internal_interface
+{
+public:
+ // construction/destruction
+ bbc_memexb20_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
+
+protected:
+ // device-level overrides
+ virtual void device_start() override;
+
+ // optional information overrides
+ virtual const tiny_rom_entry *device_rom_region() const override;
+
+ virtual bool overrides_ram() override { return true; }
+ virtual uint8_t ram_r(offs_t offset) override;
+ virtual void ram_w(offs_t offset, uint8_t data) override;
+
+private:
+ void enable_w(uint8_t data);
+ void disable_w(uint8_t data);
+
+ bool m_shadow;
+ std::unique_ptr<uint8_t[]> m_ram;
+};
+
+
+// device type definition
+DECLARE_DEVICE_TYPE(BBC_MEMEXB20, bbc_memexb20_device);
+
+
+#endif /* MAME_BUS_BBC_INTERNAL_MEMEX_H */